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  • Low-floor bus


    A low-floor bus of Volgren Optimus bodied Volvo B7RLE in Australia. A low-floor bus is a bus or trolleybus that has no steps between the ground and the floor of the bus at one or more entrances, and low floor for part or all of the passenger cabin. A bus with a partial low floor may also be referred to as a low-entry bus in some locations. "Low floor" refers to a bus deck that is accessible from the sidewalk with only a single "step" with a small height difference, caused solely by the difference between the bus deck and sidewalk. This is distinct from "high-floor", a bus deck design that requires climbing one or more steps (now known as step entrance) to access the interior floor that is placed at a higher height. Being low-floor improves the accessibility of the bus for the public, particularly the elderly and people with disabilities, including those using wheelchairs and walkers. Almost all are rear-engine, rear-wheel-drive layout with no drive shaft.

  • Mass transfer


    Mass transfer is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation. Mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase is commonly used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems. Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere, the purification of blood in the kidneys and liver, and the distillation of alcohol. In industrial processes, mass transfer operations include separation of chemical components in distillation columns, absorbers such as scrubbers or stripping, adsorbers such as activated carbon beds, and liquid-liquid extraction. Mass transfer is often coupled to additional transport processes, for instance in industrial cooling towers. These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with air.

  • High-volume low-speed fan


    A High-volume low-speed fan A high-volume low-speed (HVLS) fan is a type of mechanical fan greater than in diameter. HVLS fans are generally ceiling fans although some are pole mounted. HVLS fans move slowly and distribute large amounts of air at low rotational speed– hence the name "high volume, low speed." Typical applications for HVLS fans fall into two classifications—industrial and commercial. In industrial applications, air conditioning is often cost prohibitive or impractical. Fans installed in spaces like warehouses, barns, hangars and distribution centers can prevent heat stress, increase worker comfort and the productivity of both workers and livestock. HVLS fans are also used in commercial spaces, where air conditioning is more common, but increased air movement from ceiling fans can cost-effectively augment occupant comfort or prevent stratification. Typical commercial applications include shopping malls, churches, office buildings, airport terminal buildings, fitness centers and schools. A critical concern for many commercial spaces, like schools and libraries, is sound sensitivity and quiet operation.

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